A workshop on "Mathematical Approaches to Cardiac Arrhythmias" will be sponsored by the New York Academy of Sciences in September, 1989. The proceedings form the workshop will be published as an Annals of the Academy in 1990. The major objectives of this meeting are to identify new avenues of research and to improve our understanding of basic electrophysiological alterations leading to life-threatening arrhythmias and sudden death. The workshop will bring together leading experimental and theoretical biologists, as well as clinicians, all experts in the field of cardiac rhythmicity, and will focus primarily on the cellular and subcellular bases of cardiac arrhythmias, as well as on the application of nonlinear mathematics to the understanding of such arrhythmias. The three-day meeting will consist of the following five sessions: 1. Rate-dependent activation patterns in the heart, 2. Oscillators and cardiac pacemaker, 3. Spiral waves and three-dimensional mapping, 4. Nonlinear dynamics and chaos, 5. Fractals and the heart. The proposed speakers include those at the forefront of research of the various topics this workshop will address. They will provide a unique and in-depth coverage of the respective areas in which they have expertise, thereby maximizing the likelihood of beneficial return to other participants in the workshop. It is anticipated that new approaches will be suggested. Moreover, the workshop should set the stage for future collaborative arrangements and should lead to the development of novel conceptual frameworks describing heart rhythmicity and its alterations.